Hi

 

Having converted a doorstop Vectrix scooter last year to Nissan Leaf power sucessfully, I then sold it as it was too cumbersome for my needs. I have had knee surgery and need to get pedalling and I love the whole EV concept for clean local trips and convenience, even though I am a petrol head and have gone back to competition recently too!. So I decided a bike was the way to go but new ones to a proper spec are crazy money. I am retired so have time to assemble all the parts but as luck would have it, I bought all the stuff yesterday, an ideal bike for sale locally, only used 3 or 4 times ( was bought on a bike-to-work tax rebated scheme) at 30% of new cost http://bicycletimesmag.com/first-impres ... port-disc/. Light Alloy frame, composite alloy suspension forks and hyd disk brakes seemed to be about right for the job at hand. I expect it to be quite lively!!

Two ebay auctions ending last night won me the front hub motor kit http://www.ebay.co.uk/itm/151701379415? ... EBIDX%3AIT and the 48v 10 Ah Lipo battery with BMS and charger http://www.ebay.co.uk/itm/Electric-Bike ... fresh=true.

 

So, just on 900Euro ($1000) all in, I am set to build once the ebay items arrive from Austria and Gemany. I do have some questions to put seeking the advice of the folks on here.

 

1. Should I have some sort of a torque arm on the front fork? Spec : RST Vogue Comp SL 700, 75mm, 1pc. magnesium lower w/ disc mount and alloy steerer, Cr-Mo 28.6mm stanchions, hyd. LO and pre-load adj., spring type seal

2. Is it OK/good idea to mount the battery pack and controller in a panier bag on the back?

3. I do not wish to use the motor cut out brake levers supplied with the kit and lose the higher quailty hyraulic units fitted. Options: a kill button? Microswitch? suggestions?

 

All input most welcome.

 

Thanks

 

Pedro

Dublin

Ireland

If only you'd asked here first.I don't think that you'll like what I say, Sorry for being a bit blunt, but it's important to warn people that might want to copy you.

 

That's a nice bike. It would make a really nice electric bike with the right kit, but it's completely wasted when you add a 1000w kit like what you've bought. It's light-weight will work against you because you need strength and durability. The 1000w kit will add about 13 or 14 kg to it and change it into an electric motorcycle, which won't be pleasant to ride without power. There'es much more suitable donor bikes if that's what you want.

 

The battery is only rated at 10 amps. The 1000w controller will try and drag at least 25 amps from it, which will trip the BMS if you're lucky. You'd need to file or crimp the shunt in the controller to reduce the current to about 18 amps, which would still give you reasonable power.

 

700c forks rarely have strong drop-outs. Yours are magnesium, which is brittle and has very low fatigue resistance. If you could get full power from the motor, it would soon crack the drop-outs even if you had double torque arms, especially if you use the regen. The axle will be 14 x 10mm instead of the normal 12 x 10, so you'll have trouble getting it to sit in the drop-outs deep enough. If it were my bike, I'd change the forks for sturdy steel ones.

 

It would probably be better to install that kit on a cheap bike with a steel frame and forks. You'd need one with a disc mount on the forks so that you can fit a hydraulic brake.

 

Sorry for being so negative. It might still work. Nobody will know if I'm right until you try it. I hope for your sake that I'm wrong. Whatever you do, please let us know how you get on.

Hi D8veh. The truth is never a negative!! Thanks for taking the trouble to reply so comprehensively, I am very open to advice and guidance from those who know more than me (many)!. Where are the forks likely to "give"? I have engineering skills so reinforcement may be an option or if not I will look at steel forks! The bike cost me about £200 and it is as new, hardly used.

 

Can I ask you to explain about the shunt mod? Could I replace it with an 18Amp unit?

 

Thanks again

 

Pedro

 

These are my forks. In the top pic, it looks like they are designed to take the larger axle, note the clamp nut is sitting below centre line of rebate. The axle dropout wall thickness is 10mm. The engineer in me says it looks pretty strong but I would consider machining up some titanium or stainless torque arms to be on the safe side. I am in my 60s so not planing anything more than paved surface use! Are you moved by this D8veh? P

The drop-outs do look quite deep, but your axle centre will be about 4 mm lower. It's always a problem to get a good anchor point for torque arms. I normally take the brake side one to the disc mount if it's a side-mount caliper. It doesn't work for post-mount ones. I can't see what you have. If you make your own, they have to be an exact fit. A few degrees of rotation is enough to pop your drop-outs.

 

The controller is much easier to deal with. If you remove the end-plate, you should be able to see the shunt/s. They're normally wire bridges, like coat-hanger wire. If you're lucky, you'll have two or three. The main battery voltage goes through the shunt and there's a small voltage drop across it/them, which depends on the amount of current. The controller measures that voltage drop, so it can control the current. If you change the resistance of the shunt/s, it will cause the controller to control the current at a different level. Say you have three shunts in parallel and cut one, so no current can flow through it. The total resistance will be higher, so there will be more voltage drop, so the controller thinks the current is higher than it is. It therefore controls it to a lower level. If you do the sums, you'll find that if you cut one of three shunts, you get 2/3 the current, so a 25A controller becomes a 18.3A one.

 

If you only have one shunt, you have to increase its resistance by shaving it or crimping notches in it, in which case you need to measure the current before and after with a wattmeter or voltmeter and an external shunt.

 

You could get a replacement controller, but they tend to jump from 15A to 22A and then 25A. Your controller looks like one from Kunteng. Their sinewave controllers use current control, so you can limit the current by using the pedal assist system. Each of the five levels relates to a set current when you pedal, probably going up in 5A steps, so you can just use the pedal assist system on levels 1 to 4. You don't really need the throttle, but if you do use it, it'll pull the maximum current at full throttle. There might be the possibility that you can reprogram the maximum current through the LCD. If you read the LCD instructions, you can find it in one of the advanced parameter settings, but nobody has ever confirmed that it works. You need an external meter to measure the current beforecand after.

Great info thanks. I am sort of stuck on progress until the postman delivers the kit at least! I will be back! P

Now that I've had a closer look, it's not as bad as I first thought. It all hinges on being able to strengthen the drop-outs. Another thing while I think about it. The first washer, nut or torque arm needs to sit in the drop-out dimple without touching the edges of it, otherwise when you tighten the nut, the drop-out will pop before you even power the motor. You can get special "C" washers or file down some normal ones.

 

This is what they look like:

http://www.amazon.com/Washers-Motorized-E-bike-Electric-Bicycle/dp/B00UUDITUU

This appears to be a minor engineering challenge, provided the forks themselves are capable of handling the torsional loads, rather than something falling out!! If the forks are strong enough and the drop-outs themselves can sustain the imposed loads/forces... happy days, the rest is easily sorted! P

The Specialized Crosstrail has 700c - 29" - wheels.

 

The ebay kit is a 26" wheel one.

 

Could be a problem.

The Specialized Crosstrail has 700c - 29" - wheels.

 

The ebay kit is a 26" wheel one.

 

Could be a problem.

 

 

Problem with?

The front wheel will be smaller than the back one.

 

As it's a disc brake, it should fit.

 

Almost all bicycles have the same size wheel back and front.

 

The slight nose down aspect might not be a problem, but you will need to carry two spare tubes.

Thanks Rob, I had thought of that but when you are new to something, the danger of a major booboo is ever present!!

Thanks Rob, I had thought of that but when you are new to something, the danger of a major booboo is ever present!!

 

Pleased to hear you thought of it before buying.

 

The bottom bracket and pedals will sit slightly lower, but they will be hoiked up a bit by the bigger rear wheel, so I doubt you will notice that.

 

Just don't corner hard until you've worked out what clearance you do have on the down stroke.

 

Watch out for speed humps, too.

 

I tend to level the pedals for those and freewheel over them.

 

The handlebars can be raised one way or another if you need to.

To what level do i need to increase the battery capacity to allow a safe 25amp draw?

 

Cheers

 

P

It depends on which type of battery. Your one has low discharge rate cells. Most modern ones can do better than that.

How about if I added two of these in parallel http://www.hobbyking.com/hobbyking/store/__21374__ZIPPY_Compact_5000mAh_7S_25C_Lipo_Pack.html ?

You'd need 13S in parallel to your present battery, which means that 7S plus a 6S. A 7S pack is complicated to charge because most chargers only go to 6S. 13S is always awkward.

The front wheel will be smaller than the back one.

 

As it's a disc brake, it should fit.

 

Almost all bicycles have the same size wheel back and front.

 

The slight nose down aspect might not be a problem, but you will need to carry two spare tubes.

 

shouldn't be better to have a rear 26" motor wheel and keep the front 700C wheel? The bike would look and handle better than the other way round.

shouldn't be better to have a rear 26" motor wheel and keep the front 700C wheel? The bike would look and handle better than the other way round.

 

Agreed.

 

A handful of bikes have a bigger front wheel than back one.

 

I think it's gimmicky, but the thinking is the bigger front wheel's contact point helps grip into turns and when braking.

You'd need 13S in parallel to your present battery, which means that 7S plus a 6S. A 7S pack is complicated to charge because most chargers only go to 6S. 13S is always awkward.

 

 

Doing me best to stay with you!! Am I off-beam to think that my existing 48v charger would charge such a 13s pack?

 

P

Doing me best to stay with you!! Am I off-beam to think that my existing 48v charger would charge such a 13s pack?

 

P

No, you would need something like this and charge them in parallel .

http://www.hobbyking.co.uk/hobbyking/store/__45910__HobbyKing_8482_ECO8_150W_7A_8S_Bal_Dis_Cyc_Charger_w_acc_UK_Warehouse_.html

No, you would need something like this and charge them in parallel .

http://www.hobbyking.co.uk/hobbyking/store/__45910__HobbyKing_8482_ECO8_150W_7A_8S_Bal_Dis_Cyc_Charger_w_acc_UK_Warehouse_.html

I intend to wire these piggyback packs in series and then piggyback them to the main pack in parallel. Suggested charger would then need to charge eack piggyback unit sperately! or am I wrong? P

shouldn't be better to have a rear 26" motor wheel and keep the front 700C wheel? The bike would look and handle better than the other way round.

 

Youb are hardly suggesting that I buy a second kit? If it proves an issue, I will just get the rear wheel re-rimmed to 26"!! A little more elegant solution I think!

Lipo cells have the same voltage as your present battery, but they don't have a BMS to balance them. Therefore you need to charge them with a charger that can balance them at the same time. It's dodgy charging them with a bulk charger like the one for your other battery unless you know that they stay balanced by themselves. Even then they still need to be checked and balanced fairly frequently.

The light is starting to glow. I bought the wrong technology/spec (old) battery pack!

I will go with your suggestion d8veh to leave out the manual throttle and use max setting 4 for the pedal assist. Do I still need to have a cut-out switch?

if this proves good enough for my actual usage, happy days. If not I will add the piggyback cells with bms charging. Thanks for the education.

P